Lots of people have reported problems (such as getting 404 Not Found errors) using the SquirrelMail webmail package in their web sites created through ISPConfig 3. If you have followed the "Perfect Server" guides for ISPConfig 3, you have SquirrelMail already installed, but if you are still having the same problems, then this guide is for you. This guide explains how to configure SquirrelMail on a Debian Lenny server so that you can use it from within your web sites (created through ISPConfig).